I play in a classic rock cover band. So far I used the KPA during band rehearsals and two smaller gigs. I used to play a Marshall TSL 602, which is a pretty amp, so I wanted something lighter.
The other guitarist plays a Marshall head through a Vox 2x12 cab with pedals. I played the Kemper through Yanaha 10 with some Britt or ReampZone profiles. And one Gig my sound was ok, but not great at the other gig it was awful. It was thin without any punch. It just sounded weak. My band mates even asked me after the gig whether I wanted to continue with the Kemper or better I should go back to my Marshall.
The reason for this probably is that at small venues the audience hears directly the amp in the room sound and not the miked sound. The miked sound especially with a SM57 sounds thinner than amp in the room.
Your Kemper's Pure Cab setting can get that amp in the room sound for you. It gets rid of mic coloration. It's in the Output section as well as the Cab section of each profile, set it to 10 globally and ditch the Mics. Also see if anyone has a profile of a 2x12 DSL 602 and Pure Cab that. Might just be what your missing is your trusty old cab responses. It will also filter out the mic for your main outs so now any audience will hear exactly what your hear: amp in the room.
For thin sound I'd demo a DXR12 and see if that gets you any closer. Also try the EQ Stomp 1x12 into 4x12 cab.
I used 12's with my Kemper for years but finally went to an RCF 15". I can always dial it out the extra bottom for certain venues if need be, but if I need more it's available now.
Don't ditch the Kemper because of tone, the sound is in there you will just have to work a bit to get it right for you. Cheers!